There is no doubt that Rival is better than 105. It's more comparable to Ultegra.

However, if you prefer Shimano get 105. The performance difference from Rival isn't going to make the difference between you winning or losing a race. Shifting performance is probably the same. The real difference is about ergonomics and weight. Rival is lighter, but weight doesn't make that much of a difference.

Same with comparing it to Ultegra.